The file format through PDF 1.5 is well-supported, with the exception of the "linearized" or "optimized" output format, which this module can read but not write. Many specific aspects of the document model are not manipulable with this package (like fonts), but if the input document is correctly written, then this module will preserve the model integrity.

The PDF writing feature saves as PDF 1.4-compatible. That means that we cannot write compressed object streams. The consequence is that reading and then writing a PDF 1.5+ document may enlarge the resulting file by a fair margin.

This library grants you some power over the PDF security model. Note that applications editing PDF documents via this library MUST respect the security preferences of the document. Any violation of this respect is contrary to Adobe's intellectual property position, as stated in the reference manual at the above URL.

Technical detail regarding corrupt PDFs: This library adheres strictly to the PDF specification. Adobe's Acrobat Reader is more lenient, allowing some corrupted PDFs to be viewable. Therefore, it is possible that some PDFs may be readable by Acrobat that are illegible to this library. In particular, files which have had line endings converted to or from DOS/Windows style (i.e. CR-NL) may be rendered unusable even though Acrobat does not complain. Future library versions may relax the parser, but not yet.

Note: 'clean' as in cleansave() and cleanobject() means write a fresh PDF document. The alternative (e.g. save()) reuses the existing doc and just appends to it. Also note that 'clean' functions sort the objects numerically. If you prefer that the new PDF docs more closely resemble the old ones, call preserveOrder() before cleansave() or cleanobject().

Instantiate a new CAM::PDF object. $content can be a document in a string, a filename, or '-'. The latter indicates that the document should be read from standard input. If the document is password protected, the passwords should be passed as additional arguments. If they are not known, a boolean $prompt argument allows the programmer to suggest that the constructor prompt the user for a password. This is rudimentary prompting: passwords are in the clear on the console.

This constructor takes an optional final argument which is a hash reference. This hash can contain any of the following optional parameters:

prompt_for_password => $boolean

This is the same as the $prompt argument described above.

fault_tolerant => $boolean

This flag causes the instance to be more lenient when reading the input PDF. Currently, this only affects PDFs which cannot be successfully decrypted.

$doc->toPDF()

Serializes the data structure as a PDF document stream and returns as in a scalar.

Given a fragment of PDF page content, parse it and return an object Node. This can be called as a class method in most circumstances, but is intended as an instance method.

$doc->parseInlineImage($string)

$doc->parseInlineImage($string, $objnum)

$doc->parseInlineImage($string, $objnum, $gennum)

Given a fragment of PDF page content, parse it and return an object Node. This can be called as a class method in some cases, but is intended as an instance method.

$doc->writeInlineImage($objectnode)

This is the inverse of parseInlineImage(), intended for use only in the CAM::PDF::Content class.

$doc->parseStream($string, $objnum, $gennum, $dictnode)

This should only be used by parseObj(), or other specialized cases.

Given a fragment of PDF page content, parse it and return a stream Node. This can be called as a class method in most circumstances, but is intended as an instance method.

The dictionary Node argument is typically the body of the object Node that precedes this stream.

$doc->parseDict($string)

$doc->parseDict($string, $objnum)

$doc->parseDict($string, $objnum, $gennum)

Use parseAny() instead of this, if possible.

Given a fragment of PDF page content, parse it and return an dictionary Node. This can be called as a class method in most circumstances, but is intended as an instance method.

$doc->parseArray($string)

$doc->parseArray($string, $objnum)

$doc->parseArray($string, $objnum, $gennum)

Use parseAny() instead of this, if possible.

Given a fragment of PDF page content, parse it and return an array Node. This can be called as a class or instance method.

$doc->parseLabel($string)

$doc->parseLabel($string, $objnum)

$doc->parseLabel($string, $objnum, $gennum)

Use parseAny() instead of this, if possible.

Given a fragment of PDF page content, parse it and return a label Node. This can be called as a class or instance method.

$doc->parseRef($string)

$doc->parseRef($string, $objnum)

$doc->parseRef($string, $objnum, $gennum)

Use parseAny() instead of this, if possible.

Given a fragment of PDF page content, parse it and return a reference Node. This can be called as a class or instance method.

$doc->parseNum($string)

$doc->parseNum($string, $objnum)

$doc->parseNum($string, $objnum, $gennum)

Use parseAny() instead of this, if possible.

Given a fragment of PDF page content, parse it and return a number Node. This can be called as a class or instance method.

$doc->parseString($string)

$doc->parseString($string, $objnum)

$doc->parseString($string, $objnum, $gennum)

Use parseAny() instead of this, if possible.

Given a fragment of PDF page content, parse it and return a string Node. This can be called as a class or instance method.

$doc->parseHexString($string)

$doc->parseHexString($string, $objnum)

$doc->parseHexString($string, $objnum, $gennum)

Use parseAny() instead of this, if possible.

Given a fragment of PDF page content, parse it and return a hex string Node. This can be called as a class or instance method.

$doc->parseBoolean($string)

$doc->parseBoolean($string, $objnum)

$doc->parseBoolean($string, $objnum, $gennum)

Use parseAny() instead of this, if possible.

Given a fragment of PDF page content, parse it and return a boolean Node. This can be called as a class or instance method.

$doc->parseNull($string)

$doc->parseNull($string, $objnum)

$doc->parseNull($string, $objnum, $gennum)

Use parseAny() instead of this, if possible.

Given a fragment of PDF page content, parse it and return a null Node. This can be called as a class or instance method.

$doc->parseAny($string)

$doc->parseAny($string, $objnum)

$doc->parseAny($string, $objnum, $gennum)

Given a fragment of PDF page content, parse it and return a Node of the appropriate type. This can be called as a class or instance method.

Data Accessors

$doc->getValue($object)

For INTERNAL use

Dereference a data object, return a value. Given an node object of any kind, returns raw scalar object: hashref, arrayref, string, number. This function follows all references, and descends into all objects.

$doc->getObjValue($objectnum)

For INTERNAL use

Dereference a data object, and return a value. Behaves just like the getValue() function, but used when all you know is the object number.

$doc->dereference($objectnum)

$doc->dereference($name, $pagenum)

For INTERNAL use

Dereference a data object, return a PDF object as a node. This function makes heavy use of the internal object cache. Most (if not all) object requests should go through this function.

$name should look something like '/R12'.

$doc->getPropertyNames($pagenum)

$doc->getProperty($pagenum, $propertyname)

Each PDF page contains a list of resources that it uses (images, fonts, etc). getPropertyNames() returns an array of the names of those resources. getProperty() returns a node representing a named property (most likely a reference node).

$doc->getFont($pagenum, $fontname)

For INTERNAL use

Returns a dictionary for a given font identified by its label, referenced by page.

$doc->getFontNames($pagenum)

For INTERNAL use

Returns a list of fonts for a given page.

$doc->getFonts($pagenum)

For INTERNAL use

Returns an array of font objects for a given page.

$doc->getFontByBaseName($pagenum, $fontname)

For INTERNAL use

Returns a dictionary for a given font, referenced by page and the name of the base font.

$doc->getFontMetrics($properties $fontname)

For INTERNAL use

Returns a data structure representing the font metrics for the named font. The property list is the results of something like the following:

where the $fontlabel is something like '/Helv'. The getFontMetrics() method is useful in the cases where you've forgotten which page number you are working on (e.g. in CAM::PDF::GS), or if your property list isn't part of any page (e.g. working with form field annotation objects).

$doc->addFont($pagenum, $fontname, $fontlabel)

$doc->addFont($pagenum, $fontname, $fontlabel, $fontmetrics)

Adds a reference to the specified font to the page.

If a font metrics hash is supplied (it is required for a font other than the 14 core fonts), then it is cloned and inserted into the new font structure. Note that if those font metrics contain references (e.g. to the FontDescriptor), the referred objects are not copied -- you must do that part yourself.

Removes embedded font data, leaving font reference intact. Returns true if the font exists and 1) font is not embedded or 2) embedded data was successfully discarded. Returns false if the font does not exist, or the embedded data could not be discarded.

The optional $basefont parameter allows you to change the font. This is useful when some applications embed a standard font (see below) and give it a funny name, like SYLXNP+Helvetica. In this example, it's important to change the basename back to the standard Helvetica when de-embedding.

De-embedding the font does NOT remove it from the PDF document, it just removes references to it. To get a size reduction by throwing away unused font data, you should use the following code sometime after this method.

Just like deEmbedFont(), except that the font name parameter refers to the name of the current base font instead of the PDF label for the font.

$doc->wrapString($string, $width, $fontsize, $fontmetrics)

$doc->wrapString($string, $width, $fontsize, $pagenum, $fontlabel)

Returns an array of strings wrapped to the specified width.

$doc->getStringWidth($fontmetrics, $string)

For INTERNAL use

Returns the width of the string, using the font metrics if possible.

$doc->numPages()

Returns the number of pages in the PDF document.

$doc->getPage($pagenum)

For INTERNAL use

Returns a dictionary for a given numbered page.

$doc->getPageObjnum($pagenum)

For INTERNAL use

Return the number of the PDF object in which the specified page occurs.

$doc->getPageText($pagenum)

Extracts the text from a PDF page as a string.

$doc->getPageContentTree($pagenum)

Retrieves a parsed page content data structure, or undef if there is a syntax error or if the page does not exist.

$doc->getPageContent($pagenum)

Return a string with the layout contents of one page.

$doc->getPageDimensions($pagenum)

Returns an array of x, y, width and height numbers that define the dimensions of the specified page in points (1/72 inches). Technically, this is the MediaBox dimensions, which explains why it's possible for x and y to be non-zero, but that's a rare case.

For example, given a simple 8.5 by 11 inch page, this method will return (0,0,612,792).

This method will die() if the specified page number does not exist.

$doc->getName($object)

For INTERNAL use

Given a PDF object reference, return it's name, if it has one. This is useful for indirect references to images in particular.

Return a boolean indicating whether the Print permission is enabled on the PDF.

$doc->canModify()

Return a boolean indicating whether the Modify permission is enabled on the PDF.

$doc->canCopy()

Return a boolean indicating whether the Copy permission is enabled on the PDF.

$doc->canAdd()

Return a boolean indicating whether the Add permission is enabled on the PDF.

$doc->getFormFieldList()

Return an array of the names of all of the PDF form fields. The names are the full hierarchical names constructed as explained in the PDF reference manual. These names are useful for the fillFormFields() function.

$doc->getFormField($name)

For INTERNAL use

Return the object containing the form field definition for the specified field name. $name can be either the full name or the "short/alternate" name.

$doc->getFormFieldDict($formfieldobject)

For INTERNAL use

Return a hash reference representing the accumulated property list for a form field, including all of it's inherited properties. This should be treated as a read-only hash! It ONLY retrieves the properties it knows about.

Data/Object Manipulation

Alter the document's security information. Note that modifying these parameters must be done respecting the intellectual property of the original document. See Adobe's statement in the introduction of the reference manual.

Important Note: Most PDF readers (Acrobat, Preview.app) only offer one password field for opening documents. So, if the $ownerpass and $userpass are different, those applications cannot read the documents. (Perhaps this is a bug in CAM::PDF?)

Note: any omitted booleans default to false. So, these two are equivalent:

Replace the content of the specified page with a new version. This function is often used after the getPageContent() function and some manipulation of the returned string from that function.

If your content is a parsed tree (i.e. the result of getPageContentTree) then you should serialize it via toString first.

$doc->appendPageContent($pagenum, $content)

Add more content to the specified page. Note that this function does NOT do any page metadata work for you (like creating font objects for any newly defined fonts).

$doc->extractPages($pages...)

Remove all pages from the PDF except the specified ones. Like deletePages(), the pages can be multiple arguments, comma separated lists, ranges (open or closed).

$doc->deletePages($pages...)

Remove the specified pages from the PDF. The pages can be multiple arguments, comma separated lists, ranges (open or closed).

$doc->deletePage($pagenum)

Remove the specified page from the PDF. If the PDF has only one page, this method will fail.

$doc->decachePages($pagenum, $pagenum, ...)

Clears cached copies of the specified page data structures. This is useful if an operation has been performed that changes a page.

$doc->addPageResources($pagenum, $resourcehash)

Add the resources from the given object to the page resource dictionary. If the page does not have a resource dictionary, create one. This function avoids duplicating resources where feasible.

$doc->appendPDF($pdf)

Append pages from another PDF document to this one. No optimization is done -- the pieces are just appended and the internal table of contents is updated.

Note that this can break documents with annotations. See the appendpdf.pl script for a workaround.

$doc->prependPDF($pdf)

Just like appendPDF() except the new document is inserted on page 1 instead of at the end.

$doc->duplicatePage($pagenum)

$doc->duplicatePage($pagenum, $leaveblank)

Inserts an identical copy of the specified page into the document. The new page's number will be $pagenum + 1.

If $leaveblank is true, the new page does not get any content. Thus, the document is broken until you subsequently call setPageContent().

$doc->createStreamObject($content)

$doc->createStreamObject($content, $filter ...)

For INTERNAL use

Create a new Stream object. This object is NOT added to the document. Use the appendObject() function to do that after calling this function.

$doc->uninlineImages()

$doc->uninlineImages($pagenum)

Search the content of the specified page (or all pages if the page number is omitted) for embedded images. If there are any, replace them with indirect objects. This procedure uses heuristics to detect in-line images, and is subject to confusion in extremely rare cases of text that uses BI and ID a lot.

$doc->appendObject($doc, $objectnum, $recurse?)

$doc->appendObject($undef, $object, $recurse?)

Duplicate an object from another PDF document and add it to this document, optionally descending into the object and copying any other objects it references.

Like replaceObject(), the second form allows you to append a newly-created block to the PDF.

$doc->replaceObject($objectnum, $doc, $objectnum, $recurse?)

$doc->replaceObject($objectnum, $undef, $object)

Duplicate an object from another PDF document and insert it into this document, replacing an existing object. Optionally descend into the original object and copy any other objects it references.

If the other document is undefined, then the object to copy is taken to be an anonymous object that is not part of any other document. This is useful when you've just created that anonymous object.

$doc->deleteObject($objectnum)

Remove an object from the document. This function does NOT take care of dependencies on this object.

$doc->cleanse()

Remove unused objects. WARNING: this function breaks some PDF documents because it removes objects that are strictly part of the page model hierarchy, but which are required anyway (like some font definition objects).

$doc->createID()

For INTERNAL use

Generate a new document ID. Contrary the Adobe recommendation, this is a random number.

$doc->fillFormFields($name => $value, ...)

$doc->fillFormFields($opts_hash, $name => $value, ...)

Set the default values of PDF form fields. The name should be the full hierarchical name of the field as output by the getFormFieldList() function. The argument list can be a hash if you like. A simple way to use this function is something like this:

If the first argument is a hash reference, it is interpreted as options for how to render the filled data:

background_color =< 'none' | $gray | [$r, $g, $b]

Specify the background color for the text field.

max_autoscale_fontsize =< $size

min_autoscale_fontsize =< $size

If the form field is set to auto-size the text to fit, then you may use these options to constrain the limits of that autoscaling. Otherwise, for example, a very long string will become arbitrarily small to fit in the box.

$doc->clearFormFieldTriggers($name, $name, ...)

Disable any triggers set on data entry for the specified form field names. This is useful in the case where, for example, the data entry Javascript forbids punctuation and you want to prefill with a hyphenated word. If you don't clear the trigger, the prefill may not happen.

$doc->clearAnnotations()

Remove all annotations from the document. If form fields are encountered, their text is added to the appropriate page.

$doc->previousRevision()

If this PDF was previously saved in append mode (that is, if clean() was not invoked on it), return a new instance representing that previous version. Otherwise return void. If this is an encrypted PDF, this method assumes that previous revisions were encrypted with the same password, which may be an incorrect assumption.

$doc->allRevisions()

Accumulate CAM::PDF instances returned by previousRevision until there are no more previous revisions. Returns a list of instances from newest to oldest including this instance as the newest.

Document Writing

$doc->preserveOrder()

Try to recreate the original document as much as possible. This may help in recreating documents which use undocumented tricks of saving font information in adjacent objects.

Undo the tweaks used to make the document 'optimized'. This function is automatically called on every save or output since this library does not yet support linearized documents.

$doc->clean()

Cache all parts of the document and throw away it's old structure. This is useful for writing PDFs anew, instead of simply appending changes to the existing documents. This is called by cleansave() and cleanoutput().

$doc->needsSave()

Returns a boolean indicating whether the save() method needs to be called. Like save(), this has nothing to do with whether the document has been saved to disk, but whether the in-memory representation of the document has been serialized.

$doc->save()

Serialize the document into a single string. All changed document elements are normalized, and a new index and an updated trailer are created.

This function operates solely in memory. It DOES NOT write the document to a file. See the output() function for that.

$doc->cleansave()

Call the clean() function, then call the save() function.

$doc->output($filename)

$doc->output()

Save the document to a file. The save() function is called first to serialize the data structure. If no filename is specified, or if the filename is '-', the document is written to standard output.

Note: it is the responsibility of the application to ensure that the PDF document has either the Modify or Add permission. You can do this like the following:

Call the clean() function, then call the output() function to write a fresh copy of the document to a file.

$doc->writeObject($objnum)

Return the serialization of the specified object.

$doc->writeString($string)

Return the serialization of the specified string. Works on normal or hex strings. If encryption is desired, the string should be encrypted before being passed here.

$doc->writeAny($node)

Returns the serialization of the specified node. This handles all Node types, including object Nodes.

Document Traversing

$doc->traverse($dereference, $node, $callbackfunc, $callbackdata)

Recursive traversal of a PDF data structure.

In many cases, it's useful to apply one action to every node in an object tree. The routines below all use this traverse() function. One of the most important parameters is the first: the $dereference boolean. If true, the traversal follows reference Nodes. If false, it does not descend into reference Nodes.

Optionally, you can pass in a hashref as a final argument to reduce redundant traversing across multiple calls. Just pass in an empty hashref the first time and pass in the same hashref each time. See changeRefKeys() for an example.

$doc->decodeObject($objectnum)

For INTERNAL use

Remove any filters (like compression, etc) from a data stream indicated by the object number.

$doc->decodeAll($object)

For INTERNAL use

Remove any filters from any data stream in this object or any object referenced by it.

$doc->decodeOne($object)

$doc->decodeOne($object, $save?)

For INTERNAL use

Remove any filters from an object. The boolean flag $save (defaults to false) indicates whether this removal should be permanent or just this once. If true, the function returns success or failure. If false, the function returns the defiltered content.

$doc->fixDecode($streamdata, $filter, $params)

This is a utility method to do any tweaking after removing the filter from a data stream.

$doc->encodeObject($objectnum, $filter)

Apply the specified filter to the object.

$doc->encodeOne($object, $filter)

Apply the specified filter to the object.

$doc->setObjNum($object, $objectnum, $gennum)

Descend into an object and change all of the INTERNAL object number flags to a new number. This is just for consistency of internal accounting.

$doc->getRefList($object)

For INTERNAL use

Return an array all of objects referred to in this object.

$doc->changeRefKeys($object, $hashref)

For INTERNAL use

Renumber all references in an object.

$doc->abbrevInlineImage($object)

Contract all image keywords to inline abbreviations.

$doc->unabbrevInlineImage($object)

Expand all inline image abbreviations.

$doc->changeString($object, $hashref)

Alter all instances of a given string. The hashref is a dictionary of from-string and to-string. If the from-string looks like regex(...) then it is interpreted as a Perl regular expression and is eval'ed. Otherwise the search-and-replace is literal.

Utility functions

$doc->rangeToArray($min, $max, $list...)

Converts string lists of numbers to an array. For example,

CAM::PDF->rangeToArray(1, 15, '1,3-5,12,9', '14-', '8 - 6, -2');

becomes

(1,3,4,5,12,9,14,15,8,7,6,1,2)

$doc->trimstr($string)

Used solely for debugging. Trims a string to a max of 40 characters, handling nulls and non-Unix line endings.

$doc->copyObject($node)

Clones a node via Data::Dumper and eval().

$doc->cacheObjects()

Parses all object Nodes and stores them in the cache. This is useful for cases where you intend to do some global manipulation and want all of the data conveniently in RAM.

$doc->asciify($string)

Helper class/instance method to massage a string, cleaning up some non-ASCII problems. This is a very incomplete list. Specifically:

f-i ligatures

(R) symbol

COMPATIBILITY

This library was primarily developed against the 3rd edition of the reference (PDF v1.4) with several important updates from 4th edition (PDF v1.5). This library focuses most deeply on PDF v1.2 features. Nonetheless, it should be forward and backward compatible in the majority of cases.

PERFORMANCE

This module is written with good speed and flexibility in mind, often at the expense of memory consumption. Entire PDF documents are typically slurped into RAM. As an example, simply calling new('PDFReference15_v15.pdf') (the 13.5 MB Adobe PDF Reference V1.5 document) pushes Perl to consume 89 MB of RAM on my development machine.

SEE ALSO

There are several other PDF modules on CPAN. Below is a brief description of a few of them. If these comments are out of date, please inform me.

PDF::API2

As of v0.46.003, LGPL license.

This is the leading PDF library, in my opinion.

Excellent text and font support. This is the highest level library of the bunch, and is the most complete implementation of the Adobe PDF spec. The author is amazingly responsive and patient.

Text::PDF

As of v0.25, Artistic license.

Excellent compression support (CAM::PDF cribs off this Text::PDF feature). This has not been developed since 2003.

PDF::Reuse

As of v0.32, Artistic/GPL license, like Perl itself.

This library is not object oriented, so it can only process one PDF at a time, while storing all data in global variables. I'm not fond of it, but it's quite popular, so don't take my word for it!

CAM::PDF is the only one of these that has regression tests. Currently, CAM::PDF has test coverage of about 50%, as reported by Build testcover.

Additionally, PDFLib is a commercial package not on CPAN (www.pdflib.com). It is a C-based library with a Perl interface. It is designed for PDF creation, not for reuse.

INTERNALS

The data structure used to represent the PDF document is composed primarily of a hierarchy of Node objects. Every node in the document tree has this structure:

All of these except "stream" are directly related to the PDF data types of the same name. Streams are treated as special cases in this library since the have a non-general syntax and placement in the document body. Internally, streams are very much like strings, except that they have filters applied to them.

All objects are referenced indirectly by their numbers, as defined in the PDF document. In all cases, the dereference() function should be used to deserialize objects into their internal representation. This function is also useful for looking up named objects in the page model metadata. Every node in the hierarchy contains its object and generation number. You can think of this as a sort of a pointer back to the root of each node tree. This serves in place of a "parent" link for every node, which would be harder to maintain.

The PDF document itself is represented internally as a hash reference with many components, including the document content, the document metadata (index, trailer and root node), the object cache, and several other caches, in addition to a few assorted bookkeeping structures.

The core of the document is represented in the object cache, which is only populated as needed, thus avoiding the overhead of parsing the whole document at read time.

AUTHOR

Chris Dolan

This module was originally developed by me at Clotho Advanced Media Inc. Now I maintain it in my spare time.

ACKNOWLEDGMENTS

Thanks to all the people who have submitted bug reports over the years! I've belatedly started crediting people in the CHANGES file. Apologies to contributors I've overlooked...